Cancer – what is it?

Key points about what is cancer?

  • Cancer is when certain cells in your body grow and divide in an uncontrolled way. These cells can invade and destroy surrounding tissues.
  • Sometimes the cancerous cells can spread (metastasise) from one part of your body to another. 
  • There are more than 200 different types of cancer.
  • Find out more about treatment, and some of the common terms and related conditions.
Otupoto waterfall New Zealand Unsplash
Print this page

In most cases, the earlier the cancer is found, the more successful the treatment is. 


Surgery is one of the main treatments for cancer. If the cancer has not spread, surgery may be the only treatment you need. Read more: A guide to cancer surgery (PDF)(external link) American Cancer Society


Chemotherapy is the treatment of cancer using anti-cancer (cytotoxic) medicines. The medicines travel through your bloodstream and kill cells in your body that grow quickly, such as cancer cells. Other fast-growing normal cells are also killed, which is why these medicines cause major side effects throughout your body. However, bodies are amazing at healing and even when normal cells are damaged, they grow again. Damaged cancer cells are less likely to grow back and this is why chemotherapy can slow or cure the spread of cancer. Read more about chemotherapy. 


Radiotherapy is sometimes called radiation treatment or radiation therapy. It uses high-energy radiation to destroy cancer cells or prevent them from reproducing. Radiotherapy only affects the part of your body the beam is aimed at. Read more about radiotherapy.

Clinical trials

As part of your cancer treatment, your doctor may suggest that you consider taking part in a clinical trial. These give you access to one of the new cancer treatments being developed. Read more about clinical trials below.

Eating with cancer

Eating healthy food is important when you are well, and it is also very important when you are receiving treatment for cancer. Read more about eating well when you have cancer.

Sex and cancer

Problems from cancer or its treatment can include lowered sexual desire, physical discomfort or a change in sexual functioning, body image issues or extreme fatigue that also affects your sexuality. Read more about sex and cancer.

Pain with cancer

People who have cancer don't always have pain. However, if you have cancer and you are experiencing pain, don't accept it as a normal part of having cancer. Cancer pain can always be managed. Find out more about managing pain from cancer.

Clinical trials are a vital part of the search to find better treatments for cancer. They are conducted to test new or modified treatments and see if they are better than existing treatments.

As part of your cancer treatment, your doctor may suggest that you consider taking part in a clinical trial. You could also ask if there is a clinical trial for your particular kind of cancer. Many people all over the world have taken part in clinical trials that have resulted in improvements to cancer treatment. However, the decision to take part in a clinical trial is always yours.

Before joining a clinical trial

Before deciding whether or not to join the clinical trial, you may wish to ask your doctor the following questions:

  • What is the standard treatment if I do not participate in the trial?
  • What is the potential benefit?
  • Which treatments are being tested and why?
  • What tests are involved?
  • What are the possible risks or side effects?
  • How long will the trial last?
  • Will I need to go into hospital for treatment?
  • What will I do if any problems occur while I am in the trial?
  • If the treatment I receive in the trial is successful for my cancer, is there a possibility of carrying on with the treatment after the trial?

Randomised clinical trials

If you decide to join a randomised clinical trial, you will be given either the best existing treatment or a promising new treatment. You will be chosen at random by computer to receive one treatment or the other. Either treatment will be appropriate for your condition. In clinical trials, people’s health and progress are carefully monitored.

If you do not want to take part in a clinical trial, your doctor will discuss the best current treatment options with you.

Learn more

Clinical trials in NZ(external link) Clinical Trials NZ
Cancer clinical trials(external link) Cancer society NZ

A cancer diagnosis brings with it many words about the condition and related aspects that you may not be familiar with. Find out what they mean here. 

Abdomen – the part of your body between your chest and hips, which contains your stomach, liver, intestines, bladder and kidneys.
Acute – has a short and relatively severe course.
Adenocarcinoma – a type of lung cancer that starts in the bronchial glands, which are found in the mucous membrane lining your airways.
Adjuvant chemotherapy – treatment of cancer with drugs to aid or assist another treatment.
Alcohol ablation – injection of ethanol (alcohol) directly into a liver tumour to kill the cancer cells.
Alveoli – the tiny air sacs in your lungs.
Alopecia – hair loss, baldness.
Anaemia – having less than the normal amount of red cells in your blood.
Analgesic – a drug that relieves or improves pain.
Anastomosis – where your bowel is rejoined after a section has been removed during surgery.
Anti-emetic – a drug that prevents or reduces nausea and vomiting.
Antifungal – a drug to treat fungal infections.
Anus – the entrance to your rectum (bottom).
Asbestosis – a slow-progressing lung disease caused by asbestos. It is not a cancer.
Ascites [said 'a-sight-ease'] – fluid collecting in your abdomen and pelvis.
Atypical hyperplasia – your milk ducts contain increased numbers of abnormal cells.
Atypical naevi – moles that are large, irregular shaped and multi-coloured. They are not cancers.
Axilla – your armpit.
Axillary lymph nodes – lymph nodes in your armpit.

Barium enema – a test to look for cancer in your bowel. A white chalky liquid is put into your rectum and then x-rays are taken.
Benign – a tumour that is not malignant (cancerous) and won't spread to another part of your body.
Benign prostatic hyperplasia (BPH) – a non-cancerous enlargement of your prostate gland.
Biopsy – the removal of a small sample of tissue from your body for examination under a microscope to help diagnose a disease.
Bladder – the hollow organ that stores your urine (pee).
Bone marrow – soft, spongy tissue found in the center of most large bones that produces blood cells: white cells, red cells and platelets.
Bone scan – a picture of your bones that can show cancers, other abnormalities and infection. When a mildly radioactive substance is injected, cancerous areas of your bone pick up more of the substance than normal bone.
Brachytherapy – a form of radiation therapy where the radiation source is placed into the area of your body being treated.
Bronchi/bronchioles – bronchi are the larger tubes that carry air in your lungs. Bronchioles are the tiny tubes that carry air to the outer parts of your lungs.
Bronchiolo-alveolar cell carcinoma – a type of lung cancer that occurs in the part of your lung where air exchange takes place.
Bronchoscopy – an examination in which a tube is passed through your nose or mouth into your lungs so that they can be examined for disease and some tissue sampled, if necessary.

Carcinoma – a cancer that starts in your skin, glands and the lining of organs (epithelial tissue).
Carcinoma in situ – a malignant (cancerous) tumour that is confined to its original site.
Cells – the 'building blocks' of your body. A human is made of millions of cells, which are adapted for different functions. Cells are able to reproduce themselves exactly, unless they are abnormal or damaged like cancer cells.
Chemotherapy – the use of special (cytotoxic) drugs to treat cancer by slowing the growth of cancer cells or killing them. 
Chronic – lasting over a long period of time.
Colon – large bowel.
Colonoscope or colonoscopy – a colonoscope is a long flexible tube inserted through your rectum (bottom) into your bowel. A specialist can look through the tube to check for signs of cancer.
Colostomy – an opening in the skin of your abdomen to which your large bowel is attached. 
Complete remission – disappearance of all signs and symptoms of cancer.
CT (computerised tomography) scan – a technique for constructing pictures from cross-sections of the body, by x-raying the part of your body to be examined, from many different angles.
Crohn's disease – chronic inflammatory disease of unknown origin, usually affecting your small or large bowel or both.
Cryotherapy – liver tumours are frozen and destroyed using liquid nitrogen probes.

Dermis – the inner layer of your skin that contains the roots of your hairs, glands that produce sweat and oil, blood and lymph vessels and nerves.
Diaphragm – a dome-like sheet of muscle that divides your chest cavity from your abdomen. It is used in breathing.
Differentiation – medical term used to describe how closely cancer cells resemble normal cells.
Ducts – a small tube in your body. In your breast, the milk ducts carry milk from the milk sacs to your nipple.

 – a condition in which the alveoli of your lungs are enlarged and damaged, which reduces your lung's surface area, causing breathing difficulties.
Epidermis – the outer layer of your skin. Cells at the bottom of the epidermis (basal layer) divide in an orderly way to replace the dead cells continually worn away from the surface of your skin.
Excision – the surgical removal of tissue from your body.

Faeces – bowel motions (poo).
Familial adenomatous polyposis coli (FAP) – a condition that causes hundreds of small growths (known as polyps) in your bowel. If left untreated FAP always turns into bowel cancer. but only about 1% of bowel cancer is due to FAP.
Fine needle aspiration – a procedure in which a fine needle is used to withdraw a few cells from a tumour for biopsy.

Genes – the tiny factors that govern the way your body's cells grow and behave. Each person has a set of many thousands of genes inherited from both parents. Genes are found in every cell of your body.
Glands – an organ or group of organs that make certain fluids.
Gleason score – a system for grading prostate cancer tumours according to size and severity.
Grading – this refers to the appearance of cancer cells under the microscope.
Gray – a unit of radiation.

Haematologist – a doctor who specialises in treatment of blood diseases.
Hereditary non-polyposis colorectal cancer (HNPCC) – a condition in some families where the tendency to develop bowel cancer is inherited. Up to 5% of all bowel cancer is due to HNPCC. About 80% of people who have the gene for HNPCC will develop a bowel cancer sometime in their life.
Hormone – a chemical produced by glands in your body.
Hormone receptors – indicators on the surface of some cancer cells that suggest the cancer depends on hormones to help it grow, and that it may therefore respond to hormone treatment.
Hormone tests – laboratory tests that are done on a sample of tissue to find out whether the cancer is likely to respond to hormone treatment.
Hormone therapy – treatment using hormones.

Ileostomy – an opening in the skin of your abdomen to which your small bowel is attached.
Impotence – the inability to have an erection.
Incontinence – the loss of bladder control, or urinary leaking.
Infusion pump – some chemotherapy drugs can be given via an infusion pump, a small portable device allowing you to have your chemotherapy at home. There are several types of pumps available, all designed to deliver a measured dose of medication continuously.
Invasion – a tumour is said to be invasive if it grows into and damages the tissues around it.

Large cell carcinoma – a type of lung cancer that usually develops in your airways and is characterised by large rounded cells.
Laser therapy – involves the use of high intensity light to destroy tumour cells.
Leucocyte – general term for a white blood cell.
Linear accelerator – a machine that produces high energy x-rays and electron beams to treat cancer.
Lobectomy – a surgical operation to remove a lobe of a lung.
Lobes – the sections that make up your lungs – the left lung has 2 lobes and the right lung has 3 lobes.
Lumbar puncture – insertion of a hollow needle into your lower spinal cord to draw out fluid for diagnosis or to give drugs.
Lungs – the 2 spongy organs within your chest cavity that are made up of very large numbers of tiny air sacs (alveoli).
Lymph – a fluid that circulates in your body and helps fight infection and disease.
Lymph glands or nodes – small, kidney-shaped sacs scattered along the lymphatic system. Your lymph nodes filter lymph fluid to remove bacteria and other harmful agents, such as cancer cells. There are lymph nodes in your abdomen, neck, armpit and groin.
Lymphatic system – the lymphatic system is part of your immune system, which protects your body against 'invaders', like bacteria and parasites. The lymphatic system is a network of small lymph nodes connected by very thin lymph vessels, which branch into every part of your body. Lymph fluid flows through this system and carries cells that help to fight disease and infection.
Lymphocyte – a type of white blood cell.
Lymphoedema – swelling caused by a build-up of lymph. This happens when there is not enough draining in lymphatic vessels or lymph nodes. It can occur following some cancer treatments.

Malignant – a tumour that is cancerous and likely to spread if it is not treated.
Mammogram – an x-ray of your breast that can be used to examine a breast lump. Mammograms are also used for women without any breast changes because they may detect a breast cancer before a lump can be felt.
Mastectomy – the surgical removal of your breast.
Mediastinum – the area in your chest cavity between your lungs. It contains your heart and large blood vessels, oesophagus, trachea and many lymph nodes.
Melanocytes – pigment cells in which melanoma usually starts.
Mesothelioma – a rare cancer of the membranes around your lungs. Exposure to asbestos can cause mesothelioma.
Metastasis (plural = metastases) – a cancer that has grown in a different part of your body due to the spread of cancer cells from the original site, eg, someone with breast cancer may have metastases in their bones. This is also called secondary cancer.
Milk sacs – the gland in a woman that produces milk. Each breast consists of a number of lobes (divisions) which contain milk sacs where the milk is produced.
Myeloma – a malignant tumour composed of plasma cells of the type normally found in your bone marrow.

Neo-adjuvant chemotherapy – chemotherapy given before the primary treatment to improve the effectiveness of the treatment.
Neoplasm – a new and abnormal growth of cells, commonly used to describe cancer.
Non-small cell lung carcinoma – one of the 2 main groups of lung cancers. This group includes squamous cell carcinoma, adenocarcinoma, large cell carcinoma and bronchiolo-alveolar cell carcinoma.
Oesophagus – the tube that carries food from your throat to your stomach.
Oncologist – a doctor specialising in the study and treatment of cancer.
Oncology – an area of medicine that specialises in the treatment of cancer.
Orchidectomy/orchiectomy – surgical removal of your testes.
Ovaries – a woman has 2 ovaries, which produce the female sex hormone oestrogen and, once a month, release an egg (ovum).
Palliative treatment – controlling the symptoms of a disease rather than curing it.
Pelvic lymph node dissection – surgical removal of some lymph glands for dissection to determine if the cancer has spread.
Peritoneum – the lining of your abdomen.
PET (positron emission tomography) scan – a technique used to build up clear and detailed cross-section pictures of your body.
Plasmacytoma – a malignant tumour of plasma cells, very similar to myeloma – plasmacytomas usually develop into multiple myeloma.
Platelets – particles in your bloodstream that help with the blood clotting process. They are formed in your bone marrow.
Pleura – membranes that line your chest wall and cover your lungs.
Pleural cavity – a space, normally empty, that lies between the 2 layers of the pleura.
Pleural effusion – fluid collecting in the pleural cavity around your lung.
Pneumonectomy – a surgical operation to remove your whole lung.
Polyp – a small growth in your bowel. It can be either cancerous or not cancerous.
Polypectomy – removal of a polyp.
Primary tumour – a malignant tumour that starts in one site of your body.
Prostate-specific antigen (PSA) – a protein normally produced by prostate cells. Tests of PSA levels are used in the diagnosis and monitoring of prostate cancer. 
Prostatitis – an inflammation of your prostate.
Prosthesis – an artificial substitute for a missing part of your body, such as your breast. It may help with balance and improve appearance.

Radiation therapy/radiotherapy – the use of radiation, usually x-rays, to kill cancer cells or injure them so they cannot grow and multiply.
Radical prostatectomy – the surgical removal of your prostate gland.
Radiologist – a doctor who specialises in the use of x-rays to diagnose disease.
Rectum – the last 12–15 cm of your large bowel leading to the outside of your body (your bottom).
Recurrence/relapse – when a disease comes back after what seemed to be a cure.
Remission – the reduction or disappearance of signs or symptoms.
Resection – the surgical removal of a portion of any part of your body.
Resectoscope – an instrument to remove tissue causing obstruction in your bladder or urethra.

Sarcoma – cancer arising in connective tissue, such as muscle, cartilage or bone.
Scrotum – the external bag or pouch containing your testes.
Secondary tumour – the same as metastasis.
Sentinel node – this is the lymph node that a cancer first spreads to.
Sigmoidoscope/sigmoidoscopy – similar to a colonoscope, except the tube is short and straight and examines your lower bowel only. A flexible sigmoidoscope is sometimes used.
Small cell carcinoma – a type of lung cancer strongly associated with cigarette smoking. It spreads early and causes few initial symptoms.
Sputum – liquid coughed up from your lungs. Also known as phlegm.
Sputum cytology test – examination of sputum under a microscope to look for cancer cells.
Squamous cell carcinoma – a cancer found most commonly on skin, but also in inner linings of your body, eg, your lungs.
Staging – investigations to find out how far a cancer has progressed. This is important in planning the best treatment.
Stenting – when a tube made of metal or plastic is inserted into a duct to keep it open and prevent closure when a tumour is growing rapidly.
Stoma – the opening of a colostomy.
Stoma therapist – a registered nurse who specialises in caring for people who have stomas.

Testes/testicles – 2 egg-shaped glands that produce semen and sex hormones.
Testosterone – a male sex hormone produced by your testes which stimulates male sexual activity and the growth of other sex organs, including your prostate.
Thoracentesis – a medical procedure to draw fluid or air from your chest using a hollow needle.
Trachea (windpipe) – the pipe through which air passes to reach your lungs. The trachea starts in your neck, immediately below your voice box (larynx), and descends a few centimetres into your chest before branching to form the 2 bronchi, one of which goes into each lung.
Transurethral resection of the prostate (TURP) – surgery via your urethra to remove blockages in your urinary tract.
Transrectal ultrasound (TRUS) – an ultrasound probe inserted into your rectum so that ultrasound scans of your prostate can be made.
Tumour – a swelling or lump. Tumours can be benign (not cancerous) or malignant (cancerous).
Tumour type – this refers to the type of cells that make up the original tumour, which affects the way the cancer behaves. Each part of your body is made up of many different types of cells, so not all cancers from a particular organ behave in the same way.
Tumour stage – the stage refers to how far the tumour has spread around your body and this is one of the main factors that determine the success of treatment. There are 4 stages for each type of cancer:

    • Stage 1 refers to cancers that have not spread outside the organ where the cancer started and so might be able to be successfully treated with surgery.
    • Stage 4 means that the cancer has spread to distant parts of your body.

Ulcerative colitis – a chronic, episodic, inflammatory disease of your large bowel and rectum.
Ultrasound – sound waves of a very high frequency used to examine structures within your body.
Ureters – tubes that carry urine from each kidney to your bladder.
Urethra – a tube that carries urine from your bladder and semen from your sex glands to the outside of your body via your penis.
Urinary catheter – artificial tube inserted to drain urine (pee) from your bladder into a collecting bag. 

There are many support services and information for people affected by cancer and their family/whānau. Find out where you can get support with cancer.

Need help now?

Healthline logo in supporters block

Need to talk logo

Healthpoint logo

Credits: Healthify editorial team. Healthify is brought to you by Health Navigator Charitable Trust.

Page last updated: